Communication devices such as User Equipments (UE) are enabled to communicate wirelessly in a radio communications system, sometimes also referred to as a radio communications network, a mobile communication system, a wireless communications network, a wireless communication system, a cellular radio system or a cellular system. The communication may be performed e.g. between two user equipments, between a user equipment and a regular telephone and/or between a user equipment and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the wireless communications network.
User equipments are also known as e.g. mobile terminals, wireless terminals and/or mobile stations, mobile telephones, cellular telephones, or laptops with wireless capability, just to mention some examples. The user equipments in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity.
The wireless communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by a network node such as a Base Station (BS), e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. eNB, eNodeB, NodeB, B node, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several radio access and communication technologies. The base stations communicate over the radio interface operating on radio frequencies with the user equipments within range of the base stations.
In some RANs, several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunications System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Spécial Mobile).
In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the mobile station. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station.
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
UMTS is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipments. The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
According to 3GPP/GERAN, a user equipment has a multi-slot class, which determines the maximum transfer rate in the uplink and downlink direction. GERAN is an abbreviation for GSM EDGE Radio Access Network. EDGE is further an abbreviation for Enhanced Data rates for GSM Evolution.
Current radio communication systems are operating in so-called licensed spectrum implying that within a specific geographical region, for example a country, a certain range of frequencies is assigned to a single operator for exclusive usage.
In contrast, current wireless-Local Area Network (LAN) technologies are operating in so-called unlicensed spectrum. Within such an unlicensed spectrum, anyone is allowed to operate transmitter equipments as long as the transmission conforms to some basic requirements, such as constraints on transmit power and transmitter out-of-band emissions. Thus, within a certain geographical region there may be multiple wireless-LAN operators, operating essentially independent of each other, on the same frequency.
Operation in licensed spectrum allows for good control of the interference to which transmissions may be subject. Thus, operation in licensed spectrum allows for high-quality wireless communication even in case of relatively-high-traffic-load situations.
At the same time, in a multi-operator scenario the use of licensed spectrum leads to spectrum fragmentation as the total available spectrum has to be divided into disjoint parts, where each spectrum part is licensed to, and exclusively used by, a certain operator. In a low-traffic-load situation, a substantial part of the spectrum may then locally and instantaneously be unused as, at a certain time, one or several operators may have no active users what-so-ever within a certain area. If that spectrum could be used by other operator(s) the data rates that could instantaneously be offered by an operator may be increased, leading to an overall improved spectrum utilization. However, with conventional spectrum licensing, where each spectrum part is assigned to, and exclusively used by, a single operator, this is not possible.
For operation in unlicensed spectrum the situation is essentially the opposite. In high-traffic-load situations the use of unlicensed spectrum may lead to more unpredictable interference, difficulties to provide good quality-of-service, and, in general, degraded spectrum efficiency. In low-traffic-load situations the use of unlicensed spectrum, where the overall available spectrum is available to every operator, may allow for higher per-operator bandwidth availability, corresponding possibilities for higher data rates, and overall improved spectrum utilization.
In the scientific paper “A dynamic spectrum allocation between network operators with priority-based sharing and negotiation” (2005 IEEE 16th International Symposium on personal, indoor and mobile radio communications, 978-3-8007-2909-8/05, pages 1004-1008), a spectrum sharing algorithm is disclosed. In the spectrum sharing algorithm the priority between network operators and the priorities of multiple class services are incorporated into the spectrum sharing metric, while also accommodating the urgent bandwidth request by proposing a negotiation procedure. The proposed scheme allocates the spectrum dynamically, reflecting the long-term occupation ratio between the network operators and the priorities of multiclass services.
A drawback with prior art systems is that it is not possible to combine high robustness at high traffic load (where the use of dedicated spectrum is preferred) with high spectrum efficiency at low traffic load (where flexible spectrum sharing is preferred). The method in the paper referred to above partly addresses this drawback but is, due to the slowness of the method, only able to adapt to long-term occupation of the spectrum and is thus not able to provide good efficiency at low traffic load when the instantaneous traffic demands are varying rapidly.